Packet size and data type

[dacattack]

While conducting tests with the AsyncMqttClient library, I've discovered that sending messages larger than 5500 bytes (the exact limit is uncertain, but it's approximately around that value) is not feasible. However, I couldn't locate any options to adjust this packet size limit within the library. My expectation was to find a label similar to what exists in the PubSubClient library.

Another concern I have pertains to the necessity of transmitting messages solely as char arrays. Unfortunately, there isn't a function variant available that would allow the transmission of a uint8_t array. This particular functionality is crucial, especially when sending certain types of data—such as substantial arrays of WAV-encoded audio data captured from an I2S MEMS microphone.

It's quite likely that these two features I've highlighted can be potentially integrated in some manner so I'll be glad to hear from someone with experience on the library.
Thanks.

[luebbe]

You may want to take a look at https://github.com/bertmelis/espMqttClient, which is a plug in replacement for async-mqtt-client and much more stable.
I don't know on which device you are trying to send big messages, but you are hopefully aware that ram is not counted in GB on embedded devices? ;)

[dacattack]

I'll have a look and test that library. I was using AsyncMqttClient instead of PubSubClient because it was way faster sending packages but I found those obstacles.
I'm a electronic engineer student working on his final degree project using the ESP32 microcontroller so yeah, I have a pretty good idea about the ram usage....

[luebbe]

Good that you know. We had questions of this kind coming in, where people were obviously not aware of the difference between KB and GB ;)
espMqttClient may seem to send slower than AsyncMqttClient, but IIRC this is because Bert hast implemented correct qos handling.